Characterization of salt-water intrusion in the lower Esino Valley, Italy using a three-dimensional numerical model

A seawater-intrusion study was conducted at an oil-refinery site located on the coast in the lower Esino Valley, Italy. A steady-state density-dependent flow model was used in order to understand the position of the freshwater/salt-water interface, as influenced by the hydrogeologic structure and the presence of industrial activities and a river. Collected data and model results showed that in a large part of the area, the salt-water interface is steep and can penetrate only a few meters inland. On the other hand, close to the river mouth, seawater represents the main saline source for the aquifer. The river, in connection with the sea, can enhance seawater encroachment into the coastal aquifer; a long-term survey of river level and chloride concentrations in groundwater is recommended to further improve the physical model and to obtain a better calibration. At the refinery site, two “secondary” sources of saline water were identified and were demonstrated to have had a great influence on the presence of brackish waters in the unconfined aquifer: leakage from the fire-extinguishing system (network of pipes containing seawater) and rough sea events. This confirmed that groundwater contamination by chloride can result from means other than seawater intrusion.